Sludge is composed of solid and dissolved material in a liquid matrix. Important factors in the digestion process are the rate and extent of sludge digestion, and the extent to which water can be removed from the digested sludge. Sludge solids include both organic and inorganic material. Sludge digestion reduces the amount of organic solids in the sludge, but has no effect on the inorganic component. The biodegradable organic matter in the sludge is used as food by aerobic microorganisms (mostly bacteria) during aerobic sludge digestion. The products of this biodegradation are carbon dioxide, water and bacterial cells. As long as this food source and oxygen are readily available the aerobic bacteria continue to feed and multiply. As the removal of the non-living organic material originally present in the sludge nears completion, the microbial populations' growth rates slow until the death rate eventually exceeds the birth rate. Much of the dead bacterial cell material is then consumed by the survivors and the sludge is “digested”.
The digested sludge can be de-watered by allowing it to stand under quiescent conditions, so that the solids settle and a layer of liquid supernatant forms above the settled sludge. This liquid is returned to the wastewater treatment plant for further treatment, and the de-watered sludge is trucked to its ultimate disposal point. Clearly, the more liquid that can be separated from the sludge at this stage, the lower the trucking costs will be.
While many methods have been suggested to aid in de-watering of digested sludge, only marginal improvement has been achieved.
A further problem associated with wastewater is in the treatment of sludge and odor associated with human waste such as may be found in sceptic tanks and the like. Sceptic tanks are used frequently for residential locations and/or other remote sites and are usually required to be pumped out every two years. In other locations, such as tourist lodges and the like, the sceptic tanks must be emptied on a yearly basis. If this is not done, and in some cases even with such action, the drainage field becomes fouled and an odor results.
A further problem associated with treatment of human waste resides in the use of portable toilets which are employed as temporary toilet facilities at many different sites. One of the major problems associated with their use is that of odor suppression. Generally, the portable toilets are pumped and cleaned weekly with the holding tank having an odor suppressant placed therein. Normally, such odor suppressants utilized a perfume type component to mask the odor rather than treating the same.
A different environmental problem is that associated with the growth of algae in various locations. In particular, the growth of algae in relatively stagnant bodies of water is an enormous problem for many ponds and lakes. Not only is the algae unattractive, but certain forms of algae can cause dermatological reactions with humans.